Proper distribution of proteins and organelles is an essential property of eukaryotic cells. This "polarity" allows them to undergo processes like division, polarized growth, and differentiation. One way you can establish polarity is by directing membrane traffick. This regulation is a conserved process from yeast to mammals, so the basic principles of how that is occurring can be uncovered in yeast and then studied in more detail in animal models. I propose to study the role of phosphatidylinositol-4-phosphate (PI4P) in secretion, specifically, to evaluate its role in Myo2p activity. Myo2p is the motor protein responsible for the movement and segregation of several cellular components during the cell cycle. One of its cargoes is the secretory vesicles, that originate from the Golgi. Abundant evidence indicate that PI4P is the major PI species in the Golgi, plus we have preliminary genetic and imaging data suggesting that PI4P may play a role in Myo2p-dependent secretory vesicle transport. I plan to investigate this further by various genetic techniques, namely overexpression suppression analysis, generation and characterization of mutants, etc. Also, using modified versions of the yeast two-hybrid and conventional biochemical assays, I will try to identify the elusive secretory vesicle Myo2-receptor. My results, together with others in the lab and elsewhere, will help our understanding of how Myo2p is regulated, which is essential for the cell's survival. [unreadable] [unreadable] [unreadable]